I understand and agree. Referring to my earlier email when I stated implicit, it was my understanding that the specific PAN ID was stateful, i.e. the receiving device somehow knew as to what PAN ID the transmitting device was associated. Given that the PAN ID was understood, the receiving device could then also have known what extended address was associated with the short address.
Pat Pat Kinney Kinney Consulting LLC IEEE 802.15 WG vice chair, SC chair ISA100 co-chair, ISA100.20 chair O: +1.847.960.3715 [email protected] <mailto:[email protected]> On 9, Oct2017, at 9:17, Tero Kivinen <[email protected]> wrote: [email protected] writes: > Agreed, the security mechanism provides an implicit PAN ID. But, as to your > first point, putting the PAN ID into the header allows the receiving device to > better manage energy. If security is used, for non-TSCH modes you always need to know the extended address of the sender, even if it is using short address when sending the frame. The nonce for non-TSCH mode is generated using extended address (see section 9.3.2.1 of 802.15.4-2015). This is mandatory as the nonce needs to be tied to the sender device, as frame number is tied to the sender device. For the TSCH mode where ASN is used it is allowed to use short address to generate the nonce, but to be able to generate the nonce the recipient needs to know the PAN ID as PAN ID is part of the nonce generation when using short addresses in nonce (see section 9.3.2.2 of 802.15.4-2015). So it would be possible to make 802.15.4 lookalike protocol where PAN ID would be completely omitted, when using TSCH mode, and still use the short address in the nonce generation, but then the recipient needs to know somehow which PAN ID was used when sender generated the frame. I.e., if sender uses PAN ID of 0x1234 when generating the nonce, but do not transmit it, then recipient either needs to try all possible PAN IDs and try to decrypt the frame using all of them, or it must have prior configuration telling the PAN ID. Because of these issues, the PAN ID cannot be completely omitted in 802.15.4 frames when using short addresses. When using extended addresses there is no issue with that, as PAN ID is not used when generating the nonce, thus when using extended addresses there is a way to completely omit the PAN ID. -- [email protected] _______________________________________________ 6tisch mailing list [email protected] https://www.ietf.org/mailman/listinfo/6tisch
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